1. Field of the Invention
The present invention generally relates to a correlation spectrometer and, more particularly, to a correlation spectrometer with an electro-optical phase modulator..
2. Description of the Prior Art
Herebefore, a correlation spectrometer, used to determine the presence of one or more molecular constituents in a sample cell and their amounts, utilized a reference cell which was physically interchangeable with an empty cell, in the path of light between the sample cell and the detector. The need for mechanical interchanging of the empty cell and the reference cell in the light path has been found to be quite disadvantageous. It creates alignment and stability problems which often affect the accuracy of the measurements. Other prior correlation spectrometers use different arrangements, such as a reflecting chopper which switches a beam, a Luft cell, and a pressure modulated radiometer (PMR). With these known prior art arrangements, the measurements are often subject to sensitivity and stability limitations and to noise.
A need therefore exists for a new correlation spectrometer in which the physical interchanging of cells in the light path is eliminated. Furthermore, a need exists for a stable, sensitive correlation spectrometer with which accurate measurements of the quantities of constituents, detected to be present in the sample cell, are achievable.